Recently, the disk motor with a high power density or a high torque density has become the mainstream product in the related applications. For example, a heavy-duty scooter equipped with a mild hybrid power system has an engine and a generator/motor device like an integrated starter generator (ISG) on a range-extended electric vehicle.
The ISG is operated under a high torque density for starting or auxiliary accelerating. Generally, the ISG is operated as a motor at a percentage higher than 70% and as a generator at a percentage lower than 30% [1]. However, serious problems existing for installing the ISG or the like system include the demand in a larger accommodation space and the difficulty in heat dissipation.
In the art, the heat-dissipation methods for the integrated generators include mainly the water-cooling system and the air-cooling system. In particular, the water-cooling system is mainly designed to cool down the casing of the generator so as thereby to dissipate the heat generated by the heated copper wires and transferred to the stator.
On the other hand, the air-cooling system consisted of a plurality of heat-dissipation fins outside around the casing of the generator, a sleeve for forming a wind tunnel to include all the fins and a fan for generating an enforced airflow through the wind tunnel is to dissipate rapidly the heat generated by the generator. According to the theory of heat convection, the heat-convective coefficient for a liquid-state flow is about 100˜10000 W/m2K, while that for a gas-state flow is about 50˜250 W/m2K. Thus, by compared to the air-cooling system, the water-cooling system may provide a better heat-dissipation capacity. However, in a loading test upon a heavy-duty motorcycle equipped with a micro hybrid power system, the generator cooled by a water-cooling system may still have a temperature high to 120˜140° C. and an external temperature high to 80˜100° C. The temperature difference as above in between is obvious as high as 40° C. It implies that ill heat conduction occurs inside the generator. Thereupon, service life of the generator and the peripherals would be terribly affected so as further to limit the operation time on the vehicle.
According to a thermal resistance analysis, it is found that the terrible heat-conductive capacity inside the generator is mainly due to the thermal resistance of the peek located between the copper wires (heat source) and the stator, which the peek has a heat-conductive coefficient of 0.25 W/mK, but provides 67% of the total thermal resistance. Thereupon, the heat generated inside the generator cannot be rapidly conveyed out to the casing, such that the accumulated heat would hit the main body of the generator. As a result, the performance of the generator would be downgraded, and the insulation of the generator would be jeopardized.
To resolve the problems located by the aforesaid analysis in the thermal resistance, a single-piece or assembly-type mechanism device of a winding frame and accompanying ceramic heat conductive plates is proposed in this disclosure. The ceramic heat conductive plates obtained through a systematic design process can significantly improve the heat dissipation area of the copper wires, and greatly increase the contact thermal conductivity between the copper wires and the stator. Thereby, the temperature difference at the generator can be substantially reduced, and the capacity in heat dissipation of the generator can be significantly increased. Thus, no matter whether the air-cooling or water-cooling system is applied, the aforesaid problems in heat dissipation of electric devices can be resolved to a great extent.